Chapter 5 



Nesting Biology and Behavior of the Marbled Murrelet 



S. Kim Nelson 1 Thomas E. Hamer 2 



Abstract: We summarize courtship, incubation, feeding, fledging, 

 and flight behavior of Marbled Murrelets (Brachyramphus 

 marmoratus) using information collected at 24 nest sites in North 

 America. Chick development, vocalizations given by adults and 

 chicks at the nest, and predator avoidance behaviors are also 

 described. Marbled Murrelets initiate nesting as early as March. 

 Females lay a single egg and both adults participate in incubation, 

 exchanging duties every 24 hours at dawn. Most incubation ex- 

 changes occur before sunrise. Chicks hatch after 27-30 days. Adults 

 feed chicks single fish up to 8 times daily, but most feedings occur 

 at dawn and dusk. Dawn feeding visits occur over a wider time 

 period than incubation exchanges, with some occurring as late as 

 65 minutes after official sunrise. The timing of incubation ex- 

 changes and feeding visits are affected by weather and light condi- 

 tions, and adults arrive later on cloudy or rainy days. To minimi?^ 

 the attraction of predators, visits to the nest are inconspicuous, 

 with adults entering and exiting the nest during low light levels, 

 and primarily without vocalizations. Because of this seabird's 

 secretive behavior, our understanding of murrelet demography, 

 nest site selection, and social interactions remain limited. 



Marbled Murrelets (Brachyramphus marmoratus) are 

 unique among seabirds in that they nest in older-aged 

 coniferous forests throughout most of their range in North 

 America. Little is known about their breeding biology because 

 nest sites have only recently (1974) been discovered and 

 described (Binford and others 1975; Hamer and Nelson, this 

 volume b; Hirsch and others 1981; Nelson and Peck, in press; 

 Quinlan and Hughes 1990; Simons 1980; Singer and others 

 1991). Marbled Murrelet behavior at the nest has been 

 monitored at 24 of 52 (35 tree and 17 ground) active nests 

 since 1980; however, only a few accounts have been published 

 (Nelson and Peck, in press; Simons 1980; Singer and others 

 1991. in press). In this paper, we provide a synthesis of 

 information on murrelet behavior patterns, chick development, 

 and vocalizations recorded at these 24 nest sites. 



Methods 



We compiled all known data on Marbled Murrelet behavior 

 at active nests in North America and combined them with our 

 own studies of murrelet nests. Data were summarized from 

 two ground and five tree nests in Alaska (Hirsch and others 

 1981; Naslund. pers. comm.: Simons 1980), one tree nest in 

 British Columbia (P. Jones, pers. comm.), two tree nests in 

 Washington (Hamer and Cummins 1991 : Ritchie, pers. comm.), 



1 Research Wildlife Biologist Oregon Cooperative Wildlife Research 

 Unit. Oregon State University. Nash 104, Corvallis, OR 97331-3803 



: Research Biologist, Hamer Environmental, 2001 Highway 9, ML 

 Vernon. WA 98273 



nine tree nests in Oregon (Nelson, unpubl. data; Nelson and 

 Peck, in press), and five tree nests in California (Kerns, pers. 

 comm.; Naslund 1993a; Singer and others 1991, in press; 

 S.W. Singer, pers. comm.) (table 1). Information on pair 

 bonding and courtship are also summarized. 



Active nests were located by observing murrelets land in 

 trees, rinding eggshells on the ground and subsequently locating 

 the nest, using radio telemetry, or by incidental observations. 

 Fifteen of the nests were found during the egg stage and 9 

 during the nestling stage. Some nests were intensively 

 monitored, others only intermittently. Data recorded at many 

 nests included time and duration of incubation exchanges 

 and feeding visits, behavior of chicks and adults, flight 

 behavior, and vocalizations. Weather conditions (percent 

 clouds, precipitation, temperature, wind) were also recorded 

 for comparison with the timing and duration of murrelet 

 activity at the nest. Means, standard errors, and ranges were 

 calculated for numerical data, such as the timing of incubation 

 exchanges and feeding visits in relation to sunrise and sunset, 

 and the length of these encounters at nests. 



Results 



Pair Bonding and Courtship Behavior 



Little is known about when and how Marbled Murrelets 

 pair. Murrelets are primarily observed in groups of two 

 throughout the year, both in the forest and on the water. 

 Many pairs on the water have included a male and female, 

 and were assumed to be mated (Carter 1984; Carter and 

 Stein, this volume; Sealy 1975a). Some of these "pairs" 

 could also be composed of adults in a temporary social 

 association; this is known to occur on the water, especially 

 when birds are not feeding (Carter, pers. comm.). However, 

 we believe that Marbled Murrelets remain paired throughout 

 the year based on these year-round pair groups and data 

 from other alcids (e.g., Harris and Birkhead 1985). 



Courtship behavior has been observed on the water in 

 early spring, when some adults are still in winter plumage, 

 as well as throughout the summer. Participation in courtship 

 behaviors while in winter plumage is expected because: (1) 

 the monomorphic plumage in Marbled Murrelets in not a 

 sexually selected trait; and (2) they probably maintain strong 

 pair bonds throughout the year. During courtship, pairs join 

 closely together (<0.5 m), point their bills in the air, partially 

 lift their breasts out of the water, and swim rapidly forward 

 (Byrd and others 1974; Nelson, unpubl. data; Van Vliet, 

 pers. comm.). Pairs also dive synchronously and surface 

 within 1-3 seconds next to one another, suggesting that they 

 remain together under water (Van Vliet, pers. comm.). 

 Preceding the dive or while swimming together in courtship 



USDA Forest Service Gen. Tech. Rep. PSW-152. 1995. 



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